Definition: Photosite; Photo-site; (occ. pixelsite)

Definition: Photosite; pixel; Photosites; Photo-site; (occ: pixelsite); | Glossary entry

Definition: Photosites; photosite; Photo-site; (poss. pixelsite) 

The photosite is found on the digital image sensor in a camera. The sensor array is made up of millions of individual photosites.

Each sensor has a specific number of tiny individual sensors. Each is a photosite. For example, a Canon 5D MkII camera has a 21.1 MegaPixel full-frame digital sensor. In this case that is 5616 photosites wide by 3744 photosites high.

Clearing up a confusion?

A digital image is composed of pixels. Each pixel in an image gets its data for light intensity and colour from a corresponding ‘pixel’ on the digital image sensor.

Originally the term ‘pixel’ referred to the electric component that was sensitive to light on the sensor. Once light impacted the tiny component it excited a small electric potential that could then be detected. Thus, data on incoming light could be collected. An array of tiny sensors of this type (millions of them) can be used to form a digital image sensor for use in a camera.

Unfortunately, the use of the term pixel can seem to be confusing. It applies separately to three different things which are closely associated…

  1. the individual location on a digital image sensor of one tiny light sensitive component;
  2. the corresponding display component on a screen (a tiny LED LED | External link - opens new tab/page) which emits light showing one tiny point of light in an image to the user;
  3. the smallest individual point of light in a displayed digital image.

However, recent use of the term pixel in common parlance gives most emphasis on the pixel being on the screen, the display side of the digital image, not the sensor location.

So, increasingly, other terms are used to describe the sensor location of a component that senses incoming light. These have been variously called Photosite; Photosites; Photo-site; occasionally pixelsite(s). Each tiny photosite senses a tiny part of the light coming through the photographic lens and records data on that light.

Pixelsites are found on the digital image sensor.

The digital Image Sensor is a photo sensitive array, signal amplifier and computer. The shiny rectangle in the middle of the chip is the photo-sensitive part of the chip. It is made up of millions of individual photosites. They are minute light-sensitive points for collecting the data needed to make the image file.
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We are not aware of any official definition that clarifies these terms. However, at the time of writing there is increasing use of the term photosite on the Internet. Some manufacturers use the term Foveon_X3_sensor | External link - opens new tab/page, other writers and bloggers are using it too. We include the term in this glossary in order to help readers understand the diverse terms that apply to the sensor components of a digital image sensor. We also acknowledge that the use of language is evolving and that in the future this use of the term may not be sustained in common use. This article will be updated as necessary.

Further notes:

When a manufacturer quotes the size of the digital sensor, they use the term mega-pixels. This denotes how many pixels are created in an image generated from the data collected on the digital image sensor.

Occasionally, photosites are referred to as pixelsites. However, the derivation of the term is obscure and its use is not common.

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Damon Guy - Netkonnexion

Damon Guy (Netkonnexion)

Damon is a writer-photographer and editor of this site. He has also run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photogs.
See also: Editors ‘Bio’.
By Damon Guy see his profile on Google+.

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